Directional drilling involves the intentional deviation or steering of a drill bit to form a non-vertical wellbore that follows a desired path. The drill bit may be pointed in the direction that one wants to drill, which may be accomplished through use of a permanent bend near the drill bit in a downhole steerable mud motor, also referred to as a progressive cavity positive displacement pump. Such a mud motor connects the drillstring and the drill bit. The mud motor includes a power section comprising a rotor and stator and a transmission section. The pressure of drilling fluid, also known as mud, pumped through the drillstring from the surface, creates eccentric motion in the power section of the mud motor that is transmitted by the transmission section as concentric power to the drill bit. By pumping mud through the drillstring to the mud motor, the drill bit turns while the drillstring does not rotate, allowing the drill bit to drill in the direction that it points.
In a mud motor, a rotor generally turns within a stator to generate the power that spins the drill bit in a downhole direction. Mud motors may use different rotor and stator configurations to optimize performance for a directional drilling assembly. Non-metal materials, such as composite materials and/or resilient materials, such as elastomers, have come to be utilized in the fabrication of components in mud motors. For example, the stator of the mud motor may be formed of a composite material lined with a resilient material, such as an elastomer. However, severe operating and environmental conditions associated with oilfield applications where directional drilling assemblies may be utilized tend to degrade or induce mechanical failure of these materials forming components of mud motors due to insufficient adhesion or bonding between the materials.